A. Field of Invention
The present invention relates to wide area lighting systems which utilize a plurality of light fixtures elevated at substantial heights relative to an area or volume of space to be lighted. In particular, the present invention relates to addition of visors of specific characteristics to just selected fixtures to address playability and glare or spill light issues.
B. Issues in the Present State of the Art
A conventional and well-known way to light large areas economically is to erect several poles at spaced positions around the area to be lighted. Each pole would elevate one or more bowl-shaped reflectors, each surrounding a high intensity discharge (HID) lamp. Each fixture produces a relatively controlled and concentrated beam of light. By appropriate design and aiming of the fixtures, the beams can be directed from various directions to compositely light the target area relatively uniformly.
A primary example of such lighting is for outdoor sports fields. The owner of the present application, Musco Corporation, has been involved in such sports field lighting for many years. Their website, www.musco.com, provides information and background on such lighting.
These types of lighting systems have been successful because they are both effective and relatively economical. By efficient engineering design, the number of fixtures to effectively light the area can be minimized. Thus, cost of the system (including minimization of number of poles—which can be sometimes be the largest portion of cost of such systems) can be minimized.
However, to achieve the type of light levels for sports such as baseball, football, softball, soccer, etc., relatively powerful light sources are required. Thus, issues of glare and spill light exist with these systems. For example, a player on the field can be affected by glare caused by looking directly at one of these powerful HID light sources in a fixture. Glare, as well as spill light, relative to a homeowner across the street from the sports field can also be an issue. The issues of glare and spill light are well-known in the art. A variety of attempts have been made to address glare and spill. The owner of the present application has developed a number of systems for the same. Examples can be found at the U.S. Patent and Trademark Office under the assignee name of Musco Corporation. One specific example is U.S. Pat. No. 4,816,974 (incorporated by reference hereto). U.S. Pat. No. 4,816,974 gives some discussion of glare and spill issues and considerations, as well as general information about sports lighting and the type of fixtures commonly used. While these glare and spill light control methods have generally worked well, there usually is some balancing of factors involved in glare and spill control. For example, complete elimination of spill light to areas surrounding the field may require substantial and drastic glare and spill control measures, which could be expensive, diminish the light available to use at the field, and involve the need for additional fixtures which would increase cost. Sometimes, glare and spill is not an issue for the field, but many times it is. Sometimes effective design of the lighting system (e.g. placement of poles, number and direction of aiming of fixtures, etc.) can avoid the need for drastic glare and spill control measures. However, there are many fields that have on- or off-field situations that require attention and can not be easily eliminated. For example, there may be no option as to placement of a pole or poles, which, in turn, might result in one or more fixtures on a pole creating on-field playability issues or unavoidable glare and spill problems with a particular house or off-field location.
Another example is the fact that the light used to illuminate a field ideally provides what is called playability for the players on the field. Many times, players cannot help but be in direct line-of-sight with some fixtures. This can affect the player's ability to play the game on the field (e.g. follow the flight of a ball). One approach in the past was to block light from any offending fixture. However, this would reduce the amount of available light for the field, which could either result in insufficient light for the field or require substantial added expense to add light to the field through other fixtures or methods. Many times, therefore, the issue is ignored or not addressed.
Another playability issue applies particularly to what can be called aerial sports (e.g. where a ball, as a part of the game, can move to locations well above the field). Since typical sports lighting systems have fixtures elevated on poles around the outside of the field, and the fixtures are typically aimed down towards the field, the volume of space above the center of the field (e.g. mid-field) may have substantially less light. This can make it difficult for a player to follow a ball in flight, especially if it moves from higher illumination areas to lower, or if the player loses continuous sight of the ball and must reacquire it.
Some of the glare and spill systems of Musco Corporation, e.g. TLC™ brand, can control glare and spill very well but mid-field playability may sometimes be affected somewhat. Other glare and spill control, e.g. Musco Corporation Level-8™ for example, can provide a good combination of glare and spill control with generally adequate mid-field playability. However, there can be situations where more mid-field playability illumination is desirable.
Therefore, the present invention relates to apparatus and methods for balancing the various and sometimes complicated issues of wide area lighting to try to optimize available light to and above the field at the most economic cost, but also includes specific remedies to improve playability to players or address glare and spill issues for indicated off-field sites.